Field of the Invention
The present invention relates to a light source unit and a projector having this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as image projection systems which project a screen of a personal computer and a video image, as well as images based on image data stored on a memory card onto a screen. These projectors are such that light emitted from a light source is collected onto a micromirror display device called a digital micromirror device (DMD) or a liquid crystal panel, so that a color image is projected onto a screen for display thereon.
The application of these projectors is expanded from a presentation on a business scene to a domestic use in association with the propagation of personal computers and video equipment such as DVD players. Conventionally, in the mainstream of these projectors, high-intensity discharge lamps have been used as a light source. In recent years, however, there have been made developments of various types of projectors which use, as a light source, a plurality of semiconductor light emitting devices such as laser diodes and which include a fluorescence plate which uses the semiconductor light emitting devices as an excitation light source.
A light source unit disclosed in Japanese Unexamined Patent Publication No. 2015-232677 (Patent Literature 1) has an excitation light shining device in which a plurality of blue laser diodes are arranged into a matrix configuration and a fluorescence plate on which fluorescence material is formed. Light in the blue wavelength range which is emitted from the blue laser diodes is collected in the position where the fluorescence material is formed. The fluorescence material is excited by the light in the blue wavelength range to emit light in the green wavelength range.
In general, distances from the plurality of blue laser diodes which are disposed on the excitation light shining device to the fluorescence material on the fluorescence plate differ due to the positions of the blue laser diodes so disposed and the characteristics a light guiding member. There may be situations where in the event that lengths of optical paths of lights in the blue wavelength range which are emitted from the blue laser diodes differ, the lights shone onto the fluorescence material produce different shapes thereon depending upon the individual blue laser diodes from which the lights are originated. In the case of a plurality of blue laser diodes being used as an excitation light source as in Patent Literature 1 above, a distribution of the lights in the blue wavelength range which are superposed on one another on the fluorescence plate may become uneven in an effective range of the fluorescence plate; for example, the illuminated intensity becomes high at the center of the fluorescence plate. When the illuminated intensity becomes too high, the fluorescence efficiency of the fluorescence material is deteriorated, and in the event that the illuminated distribution is uneven, the irregularity in luminance tends to be produced easily.